Leslie graduated with a Music Major from the High School of Performing Arts, with a BA in Applied Music / Performance from the Berklee College of Music and with a degree in Music Supervision for Film / TV and Music Management from the UCLA.

In 1984 he performed the sax solos for the television drama The Three Wishes of Billy Greer. In 2006 he worked as composer on the drama Boy in a Bathtub. Leslie also worked as saxophone coach to Ralph Macchio on the movie Karate Kid and for Emma Samms on the television series The New Mike Hammer. Beside his work as technical advisor on the television series Dear John and JAG and the television movie The Kid Who Loved Christmas, he worked as music coordinator on the television series Jack and Mike, American Dreams, Pursuit of Happiness, and The Young and the Restless and feature films such as Fear No Evil, Spaceship, and Ferris Bueller's Day Off.

Leslie has been a performing member of Sha-Na-Na and is a member of The Tokens who have sold over 15 million copies worldwide of their record "The Lion Sleeps Tonight".